Please refer to FIG. 1, a side cross-sectional view illustrating the conventional image sensor package structure. In the image sensor package structure 10, an image sensor chip 12 is mounted on a substrate 11 and electrically connected to external circuits (not shown) via wires 13 and through holes 14 in the substrate 11. A frame layer 15 is disposed on the substrate 11 and surrounds the image sensor chip 12. A transparent plate 16 is mounted on the frame layer 15 so that the image sensor chip 12 is disposed in a cavity defined by the substrate 11, the frame layer 15 and the transparent plate 16. An encapsulation layer 17 covers the substrate 11, the frame layer 15 and edges of the transparent plate 16.
When the image sensor package structure 10 is put in a strict environment (high temperature and high humidity) for use or test, vapor or moisture easily enters in the cavity through the through holes 14 and small water drops are formed on a sensing surface of the image sensor chip 12 or a lower surface of the transparent plate 16. Under this condition, sensed image quality of the image sensor chip 12 is seriously affected due to the small water drops. Furthermore, the vapor or moisture floating in the cavity affects electrical performance of electrical elements in the package structure. Therefore, such influence seriously degrades the quality and reliability of the optical unit so that the image sensor package structure 10 can not meet product specification and long term use requirement.
Furthermore, the large package size of the conventional image sensor package structure 10 has been a major issue for years. Thus, the production cost cannot be reduced due to the required material consumption, abrasion of production tools and corresponding maintenance cost.
Moreover, since the encapsulation layer 17 of the image sensor package structure 10 covers a portion of an upper surface of the transparent plate 16, encapsulation material is likely to contaminate or dirty the upper surface of the transparent plate 16 during the encapsulation process. Thus, abnormal operation of the image sensor package structure 10 may occur.
Therefore, an optical package structure with higher reliability and smaller dimension without degrading the performance thereof is desired to solve the above-mentioned problem.